Intercommunicating telephone system



P 1935- c. E. LOMAX 2,053,798

INTERCOMMUNICATING TELEPHONE SYSTEM Filed May 24, 1954 AUDIBLE FREQUEN A.C. CURRENT INVENTOR CLARENCE E. LOMAX 71 ATTY' Patented Sept. 8, e 1936 UNITED STATES PATENT OFFICE INTERCOMMUNICATING TELEPHONE SYSTEM Application May 24, 1934, Serial No. 727,218

22 Claims.

This case relates to intercommunicating systems in general but more in particular to small manual telephone installations for use in hotels, apartment houses or business establishments Where an attendant is required to answer and complete telephone calls.

It is an object of the present invention to provide a telephone system of the foregoing type which is simple and reliable in operation and at the same time comprises a minimum amount of equipment.

A further object is to provide a means for answering telephone calls from another telephone when an attendant is not on duty.

An additional object is to provide a system which is arranged to provide either secret service communication, which prevents other subscribers from listening in, or common talking service at the will of the attendant.

In accordance with the above and other objects certain particular features are brought forth by the invention some of which reside in the means whereby an attendant can answer a call initiated by a regular telephone by means of a cord circuit and then complete the connection to another telephone so that in this instance the call will be on a secret basis; while if the attendant desires he can arrange the system so all telephones are on a common talking basis and calls are answered without the use of the cord circuit.

A further feature relates to circuit arrangements whereby the attendant can arrange the system so that calls can be answered simultaneously over the secret or common talking services by engaging an assistant at another telephone to aid her.

An additional feature is directed to the means whereby the attendant is signalled by a calling telephone over the common talking service in addition to the individual line lamp signal.

A particular feature relates to the provision of separate batteries for use in the secret and the common talking services to prevent cross talk between the two services.

Additional objects and features of the invention not specifically pointed out will be apparent from the specification and claims which together with the drawing illustrates an embodiment of the invention with suflicient apparatus so that a clear understanding of the same will be apparent.

- Referring to the drawing, a single cord circuit C is shown, although in actual practice several will be used; it is provided with an answering key AK for the attendants telephone B and with a signalling key SK for signalling the regular telephones such as indicated at A. Each regular telephone such as A terminates before the attendants position in a jack J together with the line lamp L. Other telephones are indicated terminating in jacks J and J before the attendants position, together with their associated line lamps L and L respectively.

An auxiliary or assistants telephone is indilo cated at D, together with its jack AJ. This telephone D may be positioned at a point some short distance from the switchboard and attendant so that when the attendant is not on duty or calls are received too fast for her to answer, 15 the assistant can answer the call at his telephone D. The auxiliary telephone is normally connected to the common talking line 3; 4, 5 and 6, while the attendants telephone B is' normally connected through key TK to the cord circuit C. 20

The substation A it will be noted is not equipped with the conventional type of gong or ringer for signalling it, but instead is provided with a neon or glow lamp N connected normally I in series with the line conductors l5 and I6 and 25 I the receiver R, and shunted out by the transmitter T when the switchhook S is raised due to the removal of the receiver R in answering or making a call. This change results in a cheaper I substation set together with other advantages 30 which will be pointed out hereinafter.

In order to enable a better understanding of the invention to be had a description will be given of the operations of the equipment which takes place when the various types of calls are made and 35 completed, and it will first be assumed that a secret service type of call is to be extended from the substation A to the substation A via the cord circuit C and the attendant B. Substation A is similar to substation A and in initiating the call 40 the receiver R is removed from the switchhook S, thereby closing a circuit extending from ground on conductor 5 contacts l8 of line jack J, line conductor 5', receiver R and transmitter T, switchhook contacts, back over line conductor I5, 45 through jack contacts l1, line lamp L, conductor 6, contacts ll] of relay 9, and the primary winding of ringing transformer TF, to battery B--2. The line lamp L is illuminated over this circuit and calls the attention of the attendant to 50 the call. In addition to the lighting of line lamp L to signal the attendant a further signalling circuit for the audible signal BZ is completed as a result of the closing of the above described circuit path. When the primary winding of the transformer TF is initially energized through'battery B2 it introduces a surge of current in the reverse direction in its secondary winding, as is well known. This surge of current passes through one winding of relay II to energize it and close its contacts I2, thereby closing a locking circuit for itself from battery B-2 to ground at release key RK. At contacts I3 relay II closes the circuit for the audible signal BZ which may take the form of a buzzer or hell. The attendant responds by inserting plug P of cord C into jack J which thereby opens the contacts II and I8 of jack J and extinguishes the line lamp L. Release key RK is operated to permit relay I I to deenergize and open the circuit of the audible signal BZ at contacts I3 as well as its locking circuit at contacts I2. The answering key AK is operated and the removal of the receiver at the attendants telephone B connects her telephone directly to the substation A through normally closed contacts of key TK, operated key AK, the plug P and jack J and the line conductors I5 and IS. The supervisory relay l which is connected in multiple with the above circuit energizes through battery B--I which battery also furnishes talking current for the above traced circuit. At its contacts 8 it closes an obvious circuit for the supervisory lamp AL to battery 3-2.

The attendant is informed of the desire of the personat substation A to be connected to substation A and thereupon inserts the opposite end of cord circuit C comprising plug P into line jack J of substation A. The plug separates contacts I! and I8 of jack J and connects the cord direct to line conductors I5 and I6. The signalling key SK is thereupon operated either intermittently or for a prolonged interval by the attendant. Alternating current of any desirable audible frequency, for example between 300 and 1,000 cycles, is thereupon extended through the primary and secondary windings of transformer TR, direct current battery B3 of a fairly high voltage which is superimposed upon the alternating current, the now closed contacts of signalling key SK, plug P and jack J, line conductors I5 and I6, and through the neon lamp N and receiver R. The direct current battery B3 in the circuit is for the purpose of ionizing the neon lamp N so the alternating current can easily pass through the lamp and also for polarizing the receiver R in case it is of the direct current type. It may be pointed out, however, that if desired the alternating current may be used without the direct current superimposed upon it, provided the voltage is suflicient to break down the neon lamp and the frequency is low enough to prevent damage to the receiver R and still render it audible. The neon lamp N is constructed so that it requires a fairly high voltage to break it down and consequently presents an open circuit to ordinary telephone voice current so that no loss in transmission efficiency is caused when a number of telephones are arranged on one line. After having been operated the neon lamp presents a very low resistance path to the ringing current and the volume of the sound emitted by this receiver is not effected or reduced at the desired audible frequency. The receiver is accordingly operated at the frequency impressed upon its diaphragm and audibly signals the person at substation A that a call is waiting to be answered. In addition to this audible signalling the illumination of the neon lamp N visibly calls attention to the call in case the person answering the same is some distance from the telephone or is slightly deaf.

These signalling arrangements at the substation therefore present distinct advantages over the ordinary gong or bell type of ringing apparatus usually employed, and in addition employ only a single item, the neon lamp for the simultaneous audible and visible signalling means.

The removal of the receiver R at substation A closes the contacts of the switchhook S and thereby connects the transmitter T in series with the receiver R and line conductors l5 and I6 and at the same time shunts out the neon lamp N. The attendant listening in on the line will be aware when the substation A answers and therefore restores the signalling key SK to disconnect the signalling current. The answer key AK is likewise restored to disconnect the attendants telephone B from the cord circuit C so that if other calls need attention it can be given over the other cord circuits. The persons at the substations A and A can now converse in complete secrecy as concerns the other subscribers, talking current being furnished through windings of relay 1 from battery B-I. The supervisory lamp AL remains lighted until both parties replace their receivers whereupon relay 7 deenergizes and extinguishes lamp AL and the attendant withdraws the plugs P and P from the jacks to restore the circuits to normal. The foregoing describes an ordinary secret service connection and as many of these connections may be completed by the attendant as there are cord circuits C available. In most instances for small installations three or four cords would suffice.

Occasionally during periods of light trafiic when her whole attention is not required to answer calls and the attendant may have other duties to perform at the switchboard; or in case all cord circuits C are in use during busy periods, the transfer key TK is operated, thereby disconnecting the attendants telephone B from the cord circuits and transferring it instead to the line conductors 3 and 4 which constitute a branch of the common talking circuit. Calls can now be made from any substation A, except those engaged in a secret service connection, to the attendants telephone B. For example should the person at substation A desire to speak to the attendant asking for information or require any of the services catered to the patrons of a hotel, the receiver R is removed to close the line loop circuit over line conductors I5 and I6, closed contacts I I and I8 of jack J, common talking line conductor 5 to ground and 6 through closed contacts I8 of relay 9, primary winding of transformer TF to battery B-2. included in series with this circuit and is illuminated to visibly call the attention of the attend ant, while as has been explained before the inductive surge of current through transformer TF energizes relay II which in turn closes the circuit of audible signal BZ at contacts I3. The attendant in responding to the call in this instance operates her key RK to disconnect the audible signal and removes the receiver from telephone B thereby closing a loop circuit extending through the telephone, contacts of operated key TK, common talking line conductor 3 to battery B2. The other side of the circuit extends over conductor 4 through low resistance relay 9, conductor 6, line lamp L, jack contacts II, line conductor I5, the substation circuit A, line conductor I6, jack contacts I 8, to conductor 5 and ground on the other side of battery B-Z. Relay 9 energizes in the above traced circuit and opens its armature spring ID from its back con- Line lamp L is also produced.

from the common talking conductors. as the battery B-l supplies current for the secret service connections and battery B--2 for the common talking connections and signalling cir- .aooavos tact, thereby removing the short circuit from around resistance RS and including the resistance in the abovetraced circuit. The line lamp L will continue to glow. The inclusion of the resistance RS in the above circuit is for the purpose of permitting the attendants telephone B to receive some current from battery 3-2 which it would be prevented from receiving ordinarily due to the comparatively low impedance of the primary winding of the transformer TF, and with this resistance the transformer TF would not shunt the current away from telephone B, whereas with the resistance shunted, enough current is fed from battery B--2 through the transformer to enable the line lamps to light brightly on the initiation of the calls.

The battery B--2 furnishes talking current to both telephone A and B and the conversation between them can proceed, the line lamp L being included in the circuit without, however, any serious eifect. 'As many other stations A as may wish to can enter in on the common talking line circuit at this time, and each will announce its presence on the line by the illumination of its associated line lamp L, and the attendant can attend to the call. Likewise, two or more substations can carry on a conversation between themselves only or with the attendant as is readily-seen from the circuit. Each time an additional substation cuts in on the common talking line it is connected in multiple with the other stations'and through its line lamp. By the use of the open circuit neon lamp N for signalling instead of the usualringer coils and condenser across eachtelephone line the impedance of the multiple connected lines is reduced to a negligible amount and an eflicient talking circuit is The connections established over the common talking circuit comprising the conductors 3 and 4, and 5 and 6 are entirely independent of the secret service connections established over the cord circuit C, because as a line jack is connected tothe cord circuit C the associated telephone line is automatically. disconnected by the cord plug Likewise wits, and as thesev batteries are separate and distinct from each other,-no interference caused by cross talk is possible between the two kinds of services.

In most establishments provided with a system of the instant type the attendant is usually provided with an assistant or clerk and in the case where the system is installed in a hotel thisclerk will take care of any errands for the hotel guests as the requests are received by the attendant. Thisclerk is usually located in the approximate vicinity of the attendants switchboardand in addition to his regular duties he is provided with a telephone D havingits line terminating in the jack AJ at the switchboard, and'extending normally to the common talking line3 and 4. With this arrangement it is possible for the assistant to answer a call by simply removing his receiver at his telephone D and answering on the common talking line at a time when the attendant isbusy answering calls on the secret service basis'or by means of the cord circuits.- This assistant at telephone D can also answer all calls when the attendant is not on duty, or the attendant can by inserting plug P in the jackAJ permit the assistant to answer a call on a 'sercret service basis over the cord circuit. In a like manner the attendant and the clerk could-both be connected to either the common talking line or the cord circuit at'the same time for conferences. In all casesit is seen that the clerk can answer all calls without going to the switchboard. All the foregoing connections are clearly understandable from the drawing and it is not thought necessary to describe in detail the different circuit connections involved.

Having described the invention, what is considered to be new and is desired to be protected by Letters Patent will be set forth in the following claims.

What-is claimed is: g r Y '1.. In a telephone system, an operators switchboard, substation lines each terminating in a jack at said switchboard, means controlled by the operator for answering calls from any line over a circuit including the line jacks, and means controlled by the operator-for answering calls from any of said lines over a common circuitseparate from any line jacks.

. 2. In a telephone system, an operator's switchboard including an operator's telephone, substationlines each terminating in a line jack at said switchboard, means for answering a call from any line by connecting the operator's telephone to said calling line jack, and means for answering a call from'any line-by only removing the receiver at the operators telephone.

3. In a telephone system, a switchboard, substation lines terminating in said switchboard, and means in said switchboard for completing calls from any of said lines on an individual basis or on a common talking basis.

4. A telephone switchboard terminating sub station lines in which calls are completed either between twosubscribers to the exclusion of all others or over a common talking system.

5; In a telephone system; an operators switchiboard, substation lines extending to said switchboard, meanscontrolled at will by the operator at said switchboard for converting the system from a common talking circuit to an individual talking circuit system when completingcalls from said lines.

- 6. In a telephone system, a main station and a plurality of substations extending to said main station, means controlled at will by said main ,station for converting said system from common talking to a system having connections exclusive to the use of two subscribers, means for completing calls from said substations over either type of system, and means for completing calls simultaneously over both types of systems.

' .7. In a telephone system, a main station, substationsextending to said main station, means "controlled at will by said station for arranging said system to complete calls on a basis where only two subscribers can converse, means for-arranging said system to complete calls on a common talking basis, and means for completing calls over both types of systems simultaneously.

8. In a telephone system, an operator's switchboard, substation lines each terminating at said switchboard in a line jack and a line lamp, means responsive to the initiation of a call from any line for operating. its associated line lamp, means for completing a secret service telephone connection with said calling line'over a circuit connection including said line jack,.and means for completing a common talking connection with any other 'calling telephone over av circuit connection including its line lamp but excluding its line jack. I

9, Ina telephone system, an operator's switchboard including a cord circuit, substation lines each terminating at said switchboard in a line jack and lamp signal, meansv for lighting said line lamp signalresponsivejto the initiation of a call from. its associated line, means responsive to the connection of said cord circuit with the. line jack tor disconnecting saidline lamp and completing. a telephone connection with said line, and means in case said cord circuit is not available for completing a telephone connection with said line independent of said line jack but including said line lamp;

10. In a telephone system, an operator's switchboard, cord circuits including an operator's telephone, substation lines each terminating in a line j ck and a line lamp signal, means responsive to the initiation of a call from any line for lighting the associated line lamp, means controlled by the operator forconnecting said cord circuit to said calling. line jack and for extinguishing the line signal in response to the call, and means cont olled at the will of the operator in response to the: call for. connecting the operator's. telephone directly to said calling line exclusive of .said cord circuit and said line jackbut including said line lamp.

11. In a telephone system, a switchboard including. cord circuits, substation lines each terminating at said switch board in a line jack, means whereby an operator in response to a. call from a. line connects a cord circuit withthe calling line jack and completes a. telephone connection, and means for completing additional telephone connections on all. lines not already connectedto cord circuits over a common talking connection.

12. In a telephone system, a switchboard having cord circuits and an operators telephone,

substation lines terminating in said switchboard, means for connecting a cord circuit with said calling line and. the operators telephone when av call is initiated and for completing a connection, an auxiliary operators telephone, and means for connecting said auxiliary telephone. with any other calling line while said operators telephone is engaged independent of any cord circuit.

13. In a telephone system, a switchboard having cord circuits and an operators telephone thereat, substation lines terminating at said switchboard,means controlled by the operator for connecting a cord circuit with a calling. line jack and with the operator's telephone to complete a secret service telephone connection, an auxiliary operator's telephone, said auxiliary telephone connected directly to any calling line independently of said line jack and said cord. circuit, and completing a common talking connection with said calling line at a time said operators telephone is engagedon said secret service connection.

. 14. .In a telephone system, a switchboard, substation lines terminating in said switchboard, means for completing calls from said lines over a connection exclusive to the calling and called subscribers and the operator, means for completing calls from said lines over a. common talking connection, and separate batteries for each type of connection.

15. In a telephonesystem, a switchboard, substation lines terminating in said switchboard, means for extending calls from said lines over individual connections, abattery for furnishing talking current for said individual connections, means for extending calls from said lines over a common talking connection, and a battery sepaces-zoo arate from said first battery for supplying talking current for said common talking connection.

16. In a telephone system, telephone lines, means for completing regular connections between said lines, means for completing common talking connections between the lines not engaged in aregular connection, and a separate battery for supplying talking current for each of said type of connections.

17.. In a telephone system, telephone lines, means for completing regular telephone connections between. any two of said lines excluding the remaining lines, means for simultaneously completing common talking telephone connections between others of said telephone lines, and a separate battery supply for each of said types of connection to prevent cross-talk between them.

18. In. a telephone system, substation lines, an individual line signal for each of said lines, a common signal for all of said lines, a ringing transformer having its primary winding connected to said lines and its secondary winding to said common. signal, means responsive to the initiation of a call from any line for lighting its associated line signal and for inducing a flow of current from the primary to the secondary windings of said ringing transformer to operate said common signal.

19. In a. telephone system, substation lines, an individual line signal for each of said lines, a common signal for all of said lines, a ringing transformer having its primary winding connected to said lines and its secondary winding to said common signal, means responsive to the initiation of a call from any line for lighting its associated line signal. and for inducing a flow of current from the primary to the secondary windings of said ringing transformer to operate said common signal, and means for locking said common signal in operatedcondition until said call is answered.

20. In a telephone system, an operator's telephone, calling lines, a signal for each of said lines, a common signal for all of said lines, a ringing transformer having its primary winding associated with all of said lines and its secondary winding'with said common signal, means responsive to the initiation of a call from any line for operating its associated line signal and for energizing said ringing transformer to induce a current flow into its secondary winding to operate said common signal, the signalling current for said call being furnished through the primary winding of said transformer, and means for connecting said operator's telephone with said calling line.

21. In a telephone system, an operator's telephone, calling lines, a signal for each of said lines, a common signal for all of said lines, a ringing transformer having its primary winding associated with all of said lines and its secondary winding with said common signal, means responsive to the initiation of a call from any line for operating its associated line signal andfor energizing said ringing transformer to induce a current flow into its secondary winding to operate said common signal, the signalling current for said call being furnished through the primary winding of said transformer, means for connecting said operators telephone with said calling line, means for furnishing talking current to said connection, and means in said connector for increasing the impedance of said transformer primary winding so said operators telephone will not be deprived of talking current.

22. in a telephone system, an operators telephone, calling lines, a line signal for each of said lines, a common signal for all of said lines, a ringing transformer having its primary winding associated with all of said lines and its secondary winding with said common signal, means responsive to the initiation of a call from any line for operating its associated line signal and for energizing said ringing transformer to induce a current flow into its secondary winding to operate said common signal, the signalling current for said call being furnished through the primary winding of said transformer, means for connecting said operator's telephone with said calling line, a resistance in said transformer primary winding, means for feeding talking current to said telephone connection, and a relay in said connection normally shunting said resistance and operated to include it in circuit with said transformer primary winding to prevent the talking current from being shunted by said winding from said operators telephone.

CLARENCE E. LOMAX. 

